The difference between hot-dip galvanized and cold-galvanized square tubes lies where?

Hot-Dip Galvanized Square Tube

A hot-dip galvanized square tube is formed by first roll-forming steel plate or steel strip into a welded square tube, and then immersing the tube in a hot-dip galvanizing bath, where a series of chemical reactions occur to form the zinc coating. The production process for hot-dip galvanized square tubes is relatively simple, yet production efficiency is high, and a wide variety of specifications are available. This type of square tube requires little equipment and capital, making it very suitable for small-scale square tube galvanizing manufacturers. However, in terms of strength, the strength of this type of steel tube is far lower than that of seamless square tubes.

Cold Galvanized Square Tube

A cold galvanized square tube uses the principle of cold galvanizing on the base square tube to provide corrosion resistance. Unlike hot-dip galvanizing, cold galvanizing coatings primarily achieve corrosion protection through electrochemical principles. Therefore, it is essential to ensure sufficient contact between the zinc powder and the steel to generate an electrode potential difference, making surface preparation of the steel very important.


Differences Between Cold and Hot-Dip Galvanized Square Tubes

Galvanized square tubes fall into two main categories:hot-dip galvanized and cold galvanized. Hot-dip galvanizing methods include wet process, dry process, lead-zinc process, and oxidation-reduction process. The main difference among these hot-dip galvanizing methods lies in the method used to activate the tube surface after acid pickling and cleaning, in order to improve galvanizing quality. In current production, the dry process and the oxidation-reduction process are predominantly used; their characteristics are shown in the table.

The zinc coating of cold galvanizing is very smooth, dense, and uniformly structured; it offers good mechanical properties and corrosion resistance; zinc consumption is 60% to 75% lower than that of hot-dip galvanizing. Electro-galvanizing involves a certain level of technical complexity, but it is necessary for applications such as single-side coating, double-side coating with different thicknesses on the inner and outer surfaces, and galvanizing thin-walled tubes.http://www.hnftsteels.com